Preheat oven to 350 degrees F (175 degrees C). Bring a large pot of salted water to a boil. Add potatoes and cook until tender, about 15 minutes. Drain and mash with milk. Meanwhile, place sausage in a large, deep skillet. Cook over medium high heat until evenly brown. Stir in green pepper and onion and cook for about 5 minutes. Fold cubed bread into potatoes, then gently fold in sausage mixture. Transfer to a 9x13 inch baking dish. Bake in preheated oven for 30 to 45 minutes, or until heated through.